Unit 4 (Ch. 6,7)

List the properties for elastic collisions

1. momentum is conserved 2. total kinetic energy is conserved 3. bouncing takes place 4. temporary deformations take place

List the properties of inelastic collisions

1. momentum is conserved 2. total kinetic energy is not conserved 3. coupling takes place 4. permanent deformations take place

A person is attracted towards the center of the earth by a 500 N gravitational force. The force of attraction of the earth towards the person is what?

500 N

The cannonball launched from a cannon with a long barrel will be faster because the cannonball receives a greater A) force B) impulse C) both D) none of these

B) impulse

The momentum change of an object is equal to the A) force acting on it. B) velocity change of the object. C) impulse acting on it. D) object's mass times the force acting on it.

C) impulse acting on it

A ping pong launcher is fired. Compared to the impulse on the ball, the amount of impulse on the launcher is A) larger B) smaller C) the same

C) the same

If the momentum of an object changes and its mass remains constant A) its velocity is changing. B) it is accelerating (or decelerating). C) there is a force acting on it. D) All of the above

D) All of the above

Skelly the skater traveling at high speed needs a certain amount of force to stop him. More stopping force will be needed if he has A) More mass V) More momentum C) Less stopping distance D) all of these

D) all of these

T or F: After a firecracker falling through the air explodes, the net momentum of its fragment decreases.

False

T or F: if the net external force acting on a system is zero, then the total momentum of the system is zero.

False

T or F: impulses are smaller when bouncing takes place

False

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?

Large truck

when an object exerts a force on a second object, the second object exerts equal and opposite forces on the first

Newton's Third Law

Superman is at rest in space when he throws an asteroid that has more mass than he does. Which moves faster, Superman or the asteroid?

Superman

why is an objects impose greater when it bounces?

The impulse required to bring an object to a stop and then throw it back again is greater than the impulse required merely to bring the object to a stop

when no net impulse acts on the object, impulse = 0

conservation of momentum

(m1 x v1i) + (m2 x v2i) = (m1 x v1f) + (m2 x v2f)

elastic collision equation

= F x t

impulse

F x t = mΔv

impulse

The product of force and time interval during which the force acts

impulse

(m1 x v1i) + (m2 x v2i) =(m1 + m2) vf

inelastic collision equation

why do internal forces not change a system but external forces cause acceleration?

internal forces cancel each other out and keep the molecules inside the system, external forces don't cancel each other out and they use the surroundings to accelerate the object

A car traveling at 100 km/h strikes a bug and splatters it. The force of impact is greater on which object?

it's the same for both

states that the absence of a net external force, the momentum of an object or system of objects is unchanged

law of conservation of momentum

inertia of motion; a tendency that keeps the object in motion

momentum

p = m x v

momentum

object B exerts a force on the object A

reaction force

Arnold Strongman and Susie Small each pull very hard on opposite ends of a rope in a tug of war. The greatest force on the rope is exerted by which person?

the force is the same for both

why does the acceleration of an action/reaction pair differ when the forces are the same?

they have different masses

Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has how much more momentum?

twice as much

What is the average momentum of a 70 kg runner who covers 400 m in 50 s?

560 kg x m/s

T or F: The padding on car dashboards lengthens the time of the passenger's impact during a collision.

True

T or F: if a net force acts on a system, the system's momentum will change.

True

why don't action forces cancel out reaction forces?

Two equal and opposite forces acting on the same object do not make an action-reaction pair

object A exerts a force on object B

action force